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This set of Digital Signal Processing Multiple Choice Questions & Answers (MCQs) focuses on “Sampling of Band Pass Signals”.

1. The frequency shift can be achieved by multiplying the band pass signal as given in equationby the quadrature carriers cos[2πFct] and sin[2πFct] and lowpass filtering the products to eliminate the signal components of 2Fc.
a) True
b) FalseView Answer

Answer: a
Explanation: It is certainly be advantageous to perform a frequency shift of the band pass signal by and sampling the equivalent low pass signal. Such a frequency shift can be achieved by multiplying the band pass signal as given in the above equation by the quadrature carriers cos[2πFct] and sin[2πFct] and low pass filtering the products to eliminate the signal components at 2Fc. Clearly, the multiplication and the subsequent filtering are first performed in the analog domain and then the outputs o f the filters are sampled.

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2. What is the final result obtained by substituting Fc=kB-B/2 , T= 1/2B and say n = 2m i.e., for even and n=2m-1 for odd in equationView Answer

9. What is the expression for low pass signal component uc(t) that can be expressed in terms of samples of the bandpass signal ?View Answer

Answer: b
Explanation: The low pass signal components uc(t) can be expressed in terms of samples of the
band pass signal as follows:

10. What is the expression for low pass signal component us(t) that can be expressed in terms of samples of the bandpass signal ?View Answer

Answer: a
Explanation: The low pass signal components us(t) can be expressed in terms of samples of the
band pass signal as follows:

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11. What is the Fourier transform of x(t) ?View Answer

Answer: d
Explanation:

12. What is the basic relationship between the spectrum o f the real band pass signal x( t ) and the spectrum of the equivalent low pass signal xl(t) ?View Answer

Answer: d
Explanation: , where Xl(F) is the Fourier transform of xl(t). This is the basic relationship between the spectrum o f the real band pass signal x ( t ) and the spectrum of the equivalent low pass signal xl(t).